Electric power steering systems generally include torque transducers for sensing torque exerted on the steering wheel by the vehicle operator and various other sensors to measure various other parameters. Typically these types of systems develop a torque assist command in response to operator exerted torque and various other vehicle parameters and this torque assist command controls current to an electric motor which provides torque assist to the vehicle steering.
The response of electric power steering systems which generate torque assist commands in response to exerted torque may vary from vehicle to vehicle or within the same vehicle as parts begin to wear. Tire load may vary in response to different road surfaces, wind conditions, driving maneuvers, and passenger loads. An operator in a vehicle with such a system will feel these changes through variations in effort required to steer the vehicle. Previous methods to compensate for these steering system variations have included adding complex circuitry and control structure to the systems to offset different variations in the system. The result is that the expense and complexity of these systems begin to outweigh the benefits.